Stent Delivery Handle With Opposite-Handed Lead Screws
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Solution Overview
Problem
Current stent graft delivery systems face challenges in accurately positioning stent grafts due to changes in effective length during deployment, as they radially expand and elastically shorten, leading to potential misalignment with the target location in the artery.
Innovation Solution
The development of handle assemblies with lead screws of opposite handedness and different pitches, which synchronize to deploy the stent graft while counteracting longitudinal displacement, ensuring precise positioning by controlling the axial position of the stent graft during deployment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a stent graft is delivered in a radially compressed, elongated state and allowed to radially expand upon delivery, then the stent graft can be delivered through a catheter and self-expand to reinforce the aorta, but the stent graft elastically shortens in the longitudinal direction, causing the effective length to change and resulting in misalignment with the target location
Solution Approach 1:
The patent applies preliminary action by pre-configuring the delivery system with a compression mechanism that anticipates and compensates for the stent graft's elastic shortening before deployment. The system pre-loads the stent graft in a compressed state within the delivery catheter, and the compression mechanism is designed to maintain this compressed state during delivery and deployment, thereby preventing the length change that would cause misalignment with the target location.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the compression force applied to the stent graft during deployment. The compression mechanism modifies the physical state of the stent graft from a compressed configuration during delivery to an expanded configuration at the target site, while controlling the transition to maintain precise positioning. This parameter change allows the stent graft to achieve its reinforcement function without suffering from uncontrolled length changes.
2Ease of manufacture
If radiopaque markers are used to establish alignment of the stent graft relative to the artery wall, then visualization during delivery is improved, but the location of the markers moves relative to the initial marker position due to the change in stent graft effective length upon deployment, leading to inaccurate positioning
Solution Approach 1:
The patent introduces an intermediary element - the compression mechanism - that acts between the stent graft and the delivery system. This intermediary maintains a constant relationship between the radiopaque markers and the target location by controlling the stent graft's length during deployment. The compression mechanism serves as a mediator that prevents the markers from moving relative to their initial positions, thereby maintaining measurement precision while preserving the visualization capability provided by the radiopaque markers.
3Shape
If the stent graft is allowed to elastically return to its natural free length upon removal from the constraining catheter, then the stent graft achieves its functional diameter for reinforcing the aorta, but the longitudinal displacement causes the stent graft to miss the target point in the artery
Solution Approach 1:
The patent applies preliminary anti-action by implementing a compression mechanism that counteracts the elastic shortening force of the stent graft before and during deployment. The mechanism pre-applies a compressive force that opposes the natural tendency of the stent graft to elongate and shorten simultaneously during radial expansion. This preliminary anti-action prevents the longitudinal displacement that would cause the stent graft to miss the target point, while still allowing the stent graft to achieve its functional diameter for effective aortic reinforcement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables accurate and precise placement of stent grafts, maintaining alignment with the target location by compensating for the change in stent length during radial expansion, thereby ensuring effective deployment and minimizing the risk of blocking adjacent arteries.
Implementation Method 1
handle assemblies with lead screws of opposite handedness and different pitches, which synchronize to deploy the stent graft while counteracting longitudinal displacement
Implementation Method 2
Upon delivery from a delivery catheter, the stent graft will radially expand and elastically shorten into its free state
Data Source
AI summary
Stent delivery systems and associated methods for delivering stents are disclosed herein. In several embodiments, a handle assembly for delivering a stent from a tubular enclosure can include a first lead screw having a first lead thread of a first pitch and first handedness, a second lead screw having a second lead thread of a second pitch and second handedness different from the first handedness, and a housing defining threads of the first and second pitches. The first lead screw can be in mechanical communication with the tubular enclosure, and the second lead screw can be in mechanical communication with the stent. Upon rotation of a portion of the housing, the housing threads can engage the lead screws so as to induce simultaneous translations of the lead screws in opposite directions. The simultaneous translations are configured to deploy the stent from the tubular enclosure.